1.Field of Invention
This invention relates to image recording apparatuses, and more particularly to an image sensor with at least one correcting lens and to a method of fabricating the same. The at least one correcting lens can shift, toward the normal line direction of the image sensor, the incident direction of light to a microlens in the edge parts of a microlens array that would otherwise overly deviate from the normal line direction.
2.Description of Related Art
In a semiconductor-type image recording apparatus like a charge-coupled device (CCD) or CMOS image recording apparatus, a microlens array is usually disposed over the array of photosensing devices to enhance the sensitivity of the same, wherein one microlens focuses light on one photosensing device.
Referring to FIG. 1 that schematically shows a part of a CMOS image recording apparatus in the prior art, a microlens array 100 is formed on a transparent base layer 10, which includes a color filter array 12 and other functional layers over a multi-level interconnect structure 20 including a first-level interconnect layer 22 and a second-level interconnect layer 24 over a photodiode array 30. The CMOS transistors are omitted in the figure for simplicity. The eyepiece 40 of the CMOS image recording apparatus is disposed above the microlens array 100, apart from the latter by a certain distance.
Because the incident direction of the light incident to a microlens 110 in an edge part, especially in a corner portion of an edge part, of the microlens array 100 overly deviates from the normal line direction of the image sensor so that light can't be focused well to the corresponding photodiode 30 directly under it, the microlens 110 is laterally displaced relative to the underlying photodiode 30 in the prior art to make the light well focus on the latter, as shown in FIG. 1. This makes the exit light 50a from the microlens 110 partially blocked by the second-level interconnect layer 24, thus lowering the recording accuracies of images.
The light-blocking issue can be solved by laterally displacing the portions of the 2nd-level interconnect layer 24 under the edge parts of the microlens array 100, but the circuit design would become much more complicated by doing so.